feat(jest-config): supports Jest config file with .mts extension

[hainenber]

Summary

Resolves #15780

This PR will allow .mts config file to be passed to Jest, enabling folks to work with native type stripping in CommonJS projects. However, full .mts support is only for Node 23.6 and above due to type stripping enabled by default. On Node version ^20.19.0 || ^22.12.0, untyped jest.config.mts would still be accepted by Jest but adding type would emit error.

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commit: 8d4363d

[fidgi]

@hainenber type stripping is also enabled by default in node 22 since version 22.18.0 (see https://nodejs.org/en/blog/release/v22.18.0)

[ahnpnl]

Hi can we get this to merge? Is it changing to .mts would help us to get through Node 22.18 strip type enabling?

[ashleybartlett]

type stripping was officially added to node 22.7.0 behind a flag --experimental-transform-types so it might work then, why v22.12 here?

Additionally, it could be that it fails when --no-experimental-strip-types is specified and within a supported version.

could this be simplified to a warning if all loader steps fail, and it's a mts file?

[hainenber]

type stripping was officially added to node 22.7.0 behind a flag --experimental-transform-types so it might work then, why v22.12 here?

22.12 is the version that can import ESM module natively, by default. You're right that users can specify experimental flags to have .mts config to be consumed but from my POV, we should guide the usage towards defaults in Node runtime instead.

[ashleybartlett]

I agree that we should direct users towards node defaults, but I think that trying to have specific version checks may not be that effective.

There is existing logic on line 48 that already determines if typestripping support is enabled in the process. Instead, could this change extend that logic, but without the fallback retry of CJS import? This may require updating jest-util to also check for .mts file extensions so it then only tries importModule on.

This approach is then more compatible with other runtimes, like Deno and Bun.

[hainenber]

I'm today-year-old to realize that there are process.feature.require_module and process.feature.typescript to test out a JS runtime's capability of loading ESM module with require and type stripping, accordingly.

I'll probably adjust this PR to reflect that. Thanks for the lead!

[cpojer]

Seems like the CI is still failing on these. Might need to disable them on older Node versions.

[SimenB]

CI is failing on multiple node versions, so I don't think the version itself is the issue. Looks like a regression?

(would love to land this 😀)

[hainenber]

PR adjusted to be JS runtime agnostic, thanks to @ashleybartlett's suggestion.

Jest should understand require(esm) and type stripping based on the JS runtime's feature flag values of process.feature.require_module and process.feature.typescript; folks can use NODE_OPTIONS to toggle on or off on demand.

Hopefully CI gods let me through.